Influenza (flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccination each year. Every year in the United States, on average:

Approximately 5 percent to 20 percent of the population gets the flu;

More than 200,000 people are hospitalized from flu complications; and

About 36,000 people die from flu.

Some people, such as older people, young children, and people with certain health conditions (such as asthma, diabetes, or heart disease), are at high risk for serious flu complications.

Symptoms of Flu

Fever (usually high)

Headache

Extreme tiredness

Dry cough

Sore throat

Runny or stuffy nose

Muscle aches

Stomach symptoms (more common in children than adults)

Complications of Flu

Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.

How Flu Spreads

Flu viruses spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose. Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 days after becoming sick. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick.

How to Prevent Flu

Take time to get a flu vaccine each year.

Flu vaccine protects against the three main flu strains that research indicates will cause the most illness.

The vaccine can make your illness milder if you become infected with a strain of virus not covered by the vaccine.

Take everyday preventive actions.

Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.

Wash your hands often with soap and water or alcohol-based hand cleaners, especially after you cough or sneeze.

Try to avoid close contact with sick people.

If you get the flu, CDC recommends that you stay home from work or school and limit contact with others to keep from infecting them.

Take flu antiviral drugs if your doctor recommends them. (They are not a substitute for vaccination.)

Antiviral drugs are prescription medicines (pills, liquid or an inhaler) that fight against the flu by keeping flu viruses from reproducing in your body.

Antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious flu complications. This could be especially important for people at high risk.